A seed test takes five minutes and answers the one question your sending dashboard cannot: where did the message actually land? Here is how to run one properly and what to do with the result.

1. Send the real thing

Test the message you are actually going to send: the same sending domain, the same template, the same links, images and footer. A hand-written plain-text note from the same account tells you nothing about how your newsletter will be treated. If you send through a newsletter tool, create a test campaign in that tool and send it to the seed list.

2. Add the identifier, nothing else

The test gives you a short code such as MP-7K3Q9XZ2. Paste it into the subject or anywhere in the body. The identifier is how the mailboxes are searched, so it must be in the message exactly as given. Do not send separate messages per recipient: one message to all seed addresses at once reproduces a normal send.

3. Start the check right after sending

Press "Check result" as soon as the message leaves. The service then polls each mailbox for five minutes. Most providers deliver within seconds; a mailbox that still shows nothing after a minute usually means greylisting, a slow queue on your side or an outright rejection.

4. Read the result by provider

Every row shows one mailbox with its placement:

  • Inbox: the message is where you want it.
  • Promotions, Social, Updates: Gmail delivered it, but into a tab. For marketing email that is normal; for transactional email it is a sign the content looks like a campaign.
  • Spam: the provider's filter rejected the message. One spam placement among several mailboxes at the same provider hints at engagement signals; spam everywhere at that provider points to reputation or authentication.
  • Not delivered: nothing arrived within the timeout. Check your sending logs for a 4xx or 5xx response from that provider.

Below the table you also see the SPF, DKIM and DMARC verdicts recorded by each receiving server, and the delivery time between the Date header and the moment the mailbox received the message.

5. Fix in the right order

  1. Authentication failures first. Nothing else matters until SPF, DKIM and DMARC pass and align.
  2. Then reputation: look up your sending IPs and domain on public blocklists and in Google Postmaster Tools.
  3. Then content: remove link shorteners, keep a healthy text-to-image ratio, use a consistent From name, and make unsubscribing obvious.
  4. Then list hygiene: remove addresses that have not engaged in months before they turn into complaints.

Re-run the test after each change. Keep the PDF reports: a history of placements per provider is the best evidence when a client or a colleague asks why open rates moved.